The disclosure of Japanese Patent Application No. HEI 11-73358 filed on Mar. 18, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a seated-state detection sensor and a passenger seat air bag device control system employing the seated-state detection sensor. In particular, the present invention relates to a seated-state detection sensor for controlling activation of a passenger seat air bag device installed in a vehicle such as an automobile, and a passenger seat air bag device control system employing the seated-state detection sensor.
2. Description of the Related Art
An example of a previously employed control apparatus for controlling activation of an air bag device installed in a vehicle such as an automobile is disclosed in Japanese Patent Application Laid-Open No. HEI 6-107114.
In the apparatus disclosed in Japanese Patent Application Laid-Open No. HEI 6-107114, an ultrasonic sensor designed as a distance sensor attached to an instrument panel is used to measure a distance from a passenger, and relative speed detection means is used to measure a relative speed between a vehicle and the passenger. A relative speed between the vehicle and the passenger at the time when the passenger contacts a steering wheel after collision is calculated based on the measured distance and relative speed. The air bag device is activated if the calculated relative speed exceeds a threshold value.
It is considered to control activation of a passenger seat air bag device by using a distance sensor similar to that disclosed in Japanese Patent Application Laid-Open No. HEI 6-107114 to measure a distance between the sensor and a passenger seated in a passenger seat. In this case, however, since the passenger seated in the passenger seat does not grasp a steering wheel which is grasped by a passenger seated in a driver seat, the passenger seated in the passenger seat can freely move his or her hands. Consequently the distance sensor may detect the hands of the passenger seated in the passenger seat. For this reason such a distance sensor has difficulty in precisely detecting forward bodily displacement of the passenger seated in the passenger seat.
It is an object of the present invention to obtain a seated-state detection sensor which is capable of precisely detecting forward bodily displacement of a passenger without being affected by movements of his or her hands, and a passenger seat air bag device control system employing the seated-state detection sensor.
In a first aspect of the present invention, a seated state detection sensor disposed in a seat cushion and divided into a plurality of parts in a longitudinal direction of a vehicle includes a seated-state detecting portion for detecting whether or not there is a passenger seated and a displacement detecting portion for detecting forward displacement of the passenger.
Thus, the presence or absence of a seated passenger can be detected by the seated-state detecting portion of the seated-state detection sensor, and forward displacement of the seated passenger can be detected by the displacement detecting portion of the seated-state detection sensor. As a result, it is possible to precisely detect forward bodily displacement of the passenger without being affected by movements of his or her hands.
In a second aspect of the present invention, a passenger seat air bag device control system includes a seated-state detection sensor disposed in a seat cushion and divided into a plurality of parts in a longitudinal direction of a vehicle. The seated-state detection sensor includes a seated-state detecting portion for detecting whether or not there is a passenger seated and a displacement detecting portion for detecting forward displacement of the passenger. The passenger seat air bag device is controlled based on a detection signal of the seated-state detection sensor.
Thus, the presence or absence of a seated passenger can be detected by the seated-state detecting portion of the seated-state detection sensor. Also, when the passenger is displaced forwardly at the time of braking as a precaution against collision, the forward displacement of the passenger can be detected by the displacement detecting portion. As a result, it is possible to precisely detect forward bodily displacement of the passenger without being affected by movements of his or her hands. Therefore, activation of the passenger seat air bag device can suitably be controlled.
In the first and second aspects, the seated-state detecting portion may be a rear portion of a plurality of divided parts of the seated-state detection sensor, and the displacement detecting portion may be a front portion of a plurality of divided parts of the seated-state detection sensor.
In the second aspect, on-to-off transition timing in the rear and front portions of the seated-state detection sensor may be measured. In this case, if an interval between the measured timings is in a predetermined time range, it is judged that the passenger has been displaced forwardly. Then activation or deactivation of the air bag device or an output level of an inflater may be controlled.
In this construction, the passenger seated in the passenger seat is displaced forwardly at the time of braking as a precaution against collision. On-to-off transition timings in the rear and front portions of the seated-state detection sensor are measured in response to the forward displacement of the passenger. If the interval between the measured timings is in a predetermined time range, it is judged that the passenger has been displaced forwardly, and activation or deactivation of the air bag device or an output level of an inflator is controlled. As a result, it is possible to precisely detect forward bodily displacement of the passenger without being affected by movements of his or her hands. Therefore, activation of the passenger seat air bag device can suitably be controlled. Further, since forward displacement of the passenger is judged based on two pieces of information obtained from the rear and front portions of the seated-state detection sensor, it is possible to avoid misjudgment and optimally control the air bag device.
In the second aspect, an interval between on-to-off transition timings of a first seated-state detection sensor constituting a rear portion of the seated-state detection sensor and a second seated-state detection sensor constituting an intermediate portion of the seated-state detection sensor and an interval between on-to-off transition timings of the second seated-state detection sensor and a third seated-state detection sensor constituting a front portion of the seated-state detection sensor may be measured. In this case, only if both the transition periods are in a predetermined time range, the air bag device is controlled to be deactivated.
In this construction, only if both the interval between the on-to-off transition timings of the first seated-state detection sensor and the second seated-state detection sensor and the interval between the on-to-off transition timings of the second seated-state detection sensor and the third seated-state detection sensor are in the predetermined time range, the air bag device is controlled to be deactivated. This, it is possible to precisely detect forward bodily displacement of the passenger and optimally control the air bag device.
In the second aspect, when the first seated-state detection sensor constituting the rear portion of the seated-state detection sensor is off and the second seated-state detection sensor constituting the intermediate portion of the seated-state detection sensor is on, it may be predicated that the passenger has been seated in a front side of a vehicle seat from the very outset. In this case, an interval between on-to-off transition timings of the second seated-state detection sensor and a third seated-state detection sensor constituting a front portion of the seated-state detection sensor is measured, and it is determined whether or not the measured interval is within a predetermined length of time. Then, the air bag device may be controlled to be deactivated.
In this construction, even if the passenger has been seated in the front portion of the seat cushion from the very outset, the interval between the on-to-off transition timings of the second seated-state detection sensor and the third seated-state detection sensor is measured, and it is determined whether or not the measured period is within a predetermined length of time, and then the air bag device is controlled to be deactivated. Therefore, it is possible to detect forward bodily displacement of the passenger with certainty and suitably control the air bag device.
In the second aspect, the rear portion of the seated-state detection sensor may set an on-signal duration period which is at least more than twice as long as an off-to-on time lag. In this case, if at least one on-signal is detected within the on-signal duration period, it is determined that there is a passenger seated.
In this construction, it is possible to prevent erroneous detection from being caused when the seated-state detection sensor is switched from on to off due to a slight bodily displacement of a passenger, for example, in the case where the vehicle travels along a rough road, or from being caused by electric noise.
In the second aspect, a detecting portion of the second seated-state detection sensor can be set to a position at a distance of 150 mm to 300 mm from a front end of the seat cushion.
In this construction, even when a child passenger is seated in the front portion of the seat cushion with his or her knees flexed, this state can be detected. Consequently, even in this case, the air bag device can be deactivated.
In a third aspect of the present invention, a seated-state detection sensor which is disposed in a seat cushion and detects whether or not there is a passenger seated includes a displacement detecting portion which is divided into a plurality of parts in a longitudinal direction of a vehicle and detects forward displacement of the passenger.
In a fourth aspect of the present invention, a passenger seat air bag device control system includes a seated-state detection sensor which is disposed in a seat cushion and detects whether or not there is a passenger seated. The seated-state detection sensor includes a displacement detecting portion which is divided into a plurality of parts in a longitudinal direction of a vehicle and detects forward displacement of the passenger. The passenger seat air bag device is controlled based on a detection signal from the seated-state detection sensor.